Slip rotation for rock drills



1936. A. G. SLATCH ER SLIP ROTATION FOR ROCK DRILLS Filed March 8, 1935 INVENTOR 5/0/096/2 In A EIEIEKMA I.

BY WIETORNEY Patented Aug. 25, 1936 SLIP ROTATION FOR. ROCK DRILLS 7 Alfred G, Slatoher, Detroit, Mich., assignor to Chicago Pneumatic Tool" Company, New York, N. Y., a corporation of NewJersey Application March 8, 1935, Serial No. 9,917

' In Great Britain August 30, 1934 6 Claims. (01. 121-7) This invention relates to. percussive toolssuch asroc-k drills, having mechanism for imparting to the drill steel a step-by-step rotary movement.

The invention is'directed to a slip rotation-clutch which permits the rifle bar to slip in case the drill steel becomes stuck or held against rotation, and thereby allows the piston to continue to reciprocate without rotating the cylinder.

The clutch mechanism in a pneumatic rock drill is usually inaccessible and incapable of adjustment; moreover it is also expensive to manufacture, and the object of this invention is to remedy these disadvantages by providing clutch mechanism which is readily accessible, capable of adjustment over a wide range, easy to assemble and cheap to manufacture.

Accordingly a percussive tool, such as a rock drill, is provided, in the back head thereof, with frictional clutch mechanism whereof the adjustment can be effected rapidly and in an extremely simple manner externally of the drill.

To this end there is associated with the rifle bar of a rock drill a clutch mechanism of the pawl-and-ratchet type with which there engages frictionally a member whereof the contiguity is capable of regulation by adjusting means protruding from the back head of the drill.

The invention is shown in one of its preferred forms in the accompanying drawing in which:

Fig. 1 is a longitudinal sectional view of a portion of a rock drill embodying the invention, the plane of the section being indicated by the arrows l-| in Fig. 2;

Fig. 2 is a fragmentary top View, certain parts being in section as indicated by the line 2--2 in Fig. 1;

Fig. 3 is a fragmentary section taken along the line 3--3 in Fig. 2; and

Fig. 4 is a fragmentary elevation looking in the direction of the arrow 4 in Fig. 2, with the bolt head removed.

Inthe embodiment disclosed, a cylinder member 'I is employed, in which is a reciprocatory piston 8 that operates on a drill steel 9 and effects the rotation thereof, being itself rotated in a manner well understood. Included in the rotating mechanism, is as usual a rifle bar I!) having a slidable interfitting engagement with a nut l l secured in the rear end of the piston 8. This rifle bar is provided at its rear end with a ratchet head I2 located in a chamber l3 formed in the back head l4 of the cylinder member 1. Surrounding the ratchet head I2 is a ratchet ring l5, also located in the chamber I3, and having internal teeth I6. The ratchet head I2 is provided with pawls llthat are adapted to engage the ratchet ring. If the ratchet ring I is held against rotation as the piston reciprocates, the pawls ll will ride the teeth '6 when said piston moves in one direction and engage behind them when the piston moves in the opposite direction, thereby rotating the piston and drill steel 9 step-by-step.

The ratchet ring I5 is held against rotation relative to the back head by friction means, adapted to yield when the torque exerted by the pawls against the ring becomes excessive. To this end, the periphery of the ratchet ring is formed with an annular groove IS. The back head H3 is provided with a pocket 20 extending tangentially of the ratchet ring. The inner extremity 2| of the pocket is screw-threaded to receive the threaded end of a bolt 22 upon which may be mounted, so as to be movable axially thereon, a frusto-conical sleeve 23 adapted to engage frictionally with the grooved periphery I9 of said ratchet'ring. A compression spring 25 is interposed between the head of the frustoconical sleeve and a non-rotatable adjusting sleeve 26, arranged upon the bolt below the head of the latter. The frusto-conical sleeve 23 has a cylindrical portion 23a telescoping within, spring 25. The sleeve may be turned about the axis of the bolt, whenever desired, in order to distribute wear on its outer surface.

The adjusting sleeve 26 fits slidably in the entrance or mouth of the pocket 2|] in the back head, and, on its outer surface it may be formed with a number of lugs 28 adapted to engage corresponding slots or recesses 29 in the underside of the head of the bolt 22. The adjusting sleeve may be prevented from rotating by means of a fiat 3|] thereon which contacts with a flat 3! formed on the back head l4 adjacent the pocket therein.

By tightening or loosening the bolt 22 and thus varying the compression of the compression spring 25, the frictional engagement between the frusto-conical sleeve and ratchet ring can be adjusted to any required degree.

What I claim is:

l. A rock drill comprising a cylinder, a piston reciprocable therein, a back head for the cylinder, rotation mechanism for rotating the piston and including a rifle bar operatively connecting the piston through pawl and ratchet mechanism to a normally stationary ring mounted in the back head, and releasable means for holding the ring against rotation relative to the back head, said means being positioned in a pocket or chamber in the back head open at one end adjacent the outside surface of the back head, said pocket being substantially tangent to the ring, said means comprising a bolt secured to the back head and extending lengthwise of the pocket, a sleeve slidable on the bolt and having an external surface tapering toward the closed end of the pocket, said external surface being in frictional engagement with the ring, and means surrounding said bolt for forcing the sleeve toward the closed end of the pocket.

2. A rock drill according to claim 1 in which the bolt is surrounded by a compression spring interposed between said sleeve and an adjusting sleeve also surrounding the bolt, said adjusting sleeve being adapted to be adjusted lengthwise of the pocket for varying the tension of the spring.

3. A rock drill according to claim 1 in which the tapered portion of the sleeve is frusto-conical and the periphery of the ring is formed. with an annular groove conforming approximately with the periphery of the engaging portion of the sleeve.

4. A rock drill comprising a cylinder providing a piston chamber, a piston reciprocable in said chamber, rotation mechanism for rotating the piston and including a rifle bar operatively connecting the piston through pawl and ratchet mechanism to a ring mounted in the drill in back of the piston chamber, and releasable means for holding the ring against rotation relative to the cylinder, said means being positioned in a pocket or chamber in the drill open at one end adjacent the outside surface of the drill, and said means comprising a holding element in the pocket adapted to engage the ring for holding the latter against rotation, said holding element being removable from the drill by movement in a straight line to the open end of the pocket.

5. A percussive tool according to claim 4 which includes means for guiding the holding element to move in a straight line tangential to the ring, and in which the holding element has a tapered surface engaging the ring to form a wedge.

6. A percussive tool according to claim 4 which comprises a bolt secured to the drill and extending substantially tangent to the ring, and in which the holding element is slidably mounted on said bolt and has a tapered surface cooperating with the ring to form a wedge.

ALFRED G. SLATCHER. 

